In recent years, different types of networks for wireless communication have been developed to provide radio communication for various wireless terminals in different areas. The wireless communication networks are constantly improved to provide better capacity, performance and coverage to meet the demands from subscribers using services and increasingly advanced terminals, such as smartphones and tablets, which often require considerable amounts of bandwidth and resources for data transport in the networks. Therefore, it is often a challenge to minimize or reduce the amount of signaling between base stations in the wireless communication network and various wireless devices being connected to the base stations for radio communication.
In this field, the term “wireless device” is commonly used and will be used in this disclosure to represent any wireless communication entity capable of radio communication including receiving downlink signals transmitted from a serving base station and sending uplink signals to the base station. Another common term is “User Equipment, UE” which implies that the communication entity can be held and operated by a human user such as a mobile telephone. However, a wireless device in this context is not necessarily held and operated by a human user. It could also be a machine-to-machine type of device operating automatically such as a sensor, counter or measuring entity.
Further, the term “base station”, also commonly referred to as a network node, radio node, e-nodeB, eNB, NB, base transceiver station, etc., represents any node of a wireless communication network that is arranged to communicate uplink and downlink radio signals with wireless devices. The base stations described here may, without limitation, include so-called macro nodes or base stations and low power nodes or base stations such as micro, pico, femto, Wifi and relay nodes or base stations, to mention some customary examples. Throughout this disclosure, the terms “network node” and “User Equipment, UE” could further be used instead of base station and wireless device, respectively.
As indicated above, it is generally of interest to keep the amount of signaling between wireless devices and base stations as low as possible, although without losing functionality, in order to save radio resources that are much needed for communication of data over radio to serve the wireless devices with various services involving transfer of data to and from the wireless devices. Such signaling includes communication of configuration messages from the network to the wireless devices containing various radio parameters dictating how the wireless device should act or behave during radio communication. Some of these radio parameters may pertain to how and/or when measurements of radio signals shall be performed by the wireless device e.g. to evaluate its current connection with a serving base station and also potential connections with other nearby target base stations. Further radio parameters in a configuration message may pertain to how and/or when the wireless device's measurements should be reported to the serving base station, and to other communication specifics related to transmission schemes, encoding, modulation, and so forth.
In a network that employs Long Term Evolution, LTE, as defined by the Third Generation Partnership Project, 3GPP, a wireless device can be in either CONNECTED mode or IDLE mode. In short, the wireless device is able to communicate data with a base station when it is in the CONNECTED mode while it just monitors various information and messages transmitted from the network when the wireless device is in the IDLE mode. In the CONNECTED mode, a protocol called Radio Resource Control, RRC, is employed which is defined in the LTE standard according to the document 3GPP TS 36.331. Whenever a wireless device enters the CONNECTED mode and becomes connected to a serving base station, i.e. a base station of a serving cell, for performing a radio communication, the serving base station transmits a control message to the wireless device containing an RRC configuration applicable for the wireless device, thus comprising a plurality of radio parameters that the wireless device is thereby instructed to apply in the radio communication, e.g. as exemplified above. This control message may be communicated by broadcast signaling to any wireless devices, multicast signaling to a specific set of wireless devices and/or unicast signaling to a single specific wireless device.
When a wireless device is in CONNECTED mode, an RRC connection is thus maintained with the currently serving base station or serving cell. Some common and rather static RRC related radio parameters, which are applicable to many wireless devices, may be communicated in a System Information Block called SIB2 using an information element called radioResourceConfigCommon. Dedicated RRC configurations are sent to a specific wireless device, either at RRC connection setup, e.g. when the wireless device switches from IDLE to CONNECTED mode, or at RRC re-establishment, e.g. when the wireless device recovers from a Radio Link Failure, or at RRC Connection Reconfiguration, e.g. after a handover to another cell and serving base station.
However, it is a problem that the above-described configuration messages can be quite large containing a considerable amount of information elements which consume radio resources when communicated to the wireless devices. Further, these large RRC configuration messages are typically communicated to each wireless device at several occasions, such as exemplified above. As a result, the capacity and performance in the network for data communication may suffer greatly due to the communication of such RRC configuration messages to multiple wireless devices, which thus occupy considerable bandwidth in the radio interface. FIG. 1 illustrates this situation where a wireless device 100 is in radio communication when first connected to a serving base station 102 which communicates an RRC configuration C1 to the wireless device 100 to dictate the wireless device's behavior.
While the wireless device 100 remains in connection with base station 102, the latter may decide that the wireless device's behavior needs to change, e.g. due to changing conditions such as increased traffic, to improve performance and efficiency in the network and/or for the wireless device. The base station 102 therefore communicates another RRC configuration C1′ to the wireless device 100 in an RRC message to carry out RRC Connection Reconfiguration, where one or more radio parameters in C1′ are different than in C1, to dictate the wanted modification of wireless device behavior. For example, the new RRC configuration C1′ may comprise a modified radio parameter that results in a handover to another base station thereby off-loading the base station 102. When the RRC configuration C1′ is communicated to the wireless device 100, it overrides the RRC configuration C1 in the wireless device 100. For various reasons, the base station 102 may communicate different RRC configurations to the wireless device 100 at different occasions which generates much signaling traffic since each RRC configuration is quite large.
FIG. 1 further illustrates that the wireless device 100 is handed over to another base station 104 which then communicates an RRC configuration C2 to the wireless device 100 to dictate the wireless device's behavior in the cell of base station 104. The base station 104 may likewise communicate multiple RRC configurations C2, C2′ . . . to the wireless device 100 at different occasions as long as the wireless device 100 remains connected to the base station 104. The same situation may occur when the wireless device 100 is further handed over to another base station 106 which then communicates one or more RRC configurations C3, C3′ . . . to the wireless device 100 to dictate the wireless device's behavior while in the cell of base station 106, and so forth. Each time a new RRC configuration is communicated to the wireless device 100, it overrides the existing RRC configuration in the wireless device 100. It can thus be understood that the current solution, as exemplified in FIG. 1, generates many RRC configuration messages from the network to different wireless devices which consumes precious bandwidth on the radio interface.